The instant invention relates generally to telecommunications and more specifically it relates to an audible interface device which provides a circuit that can detect and indicate a transmission sent exclusively to a vehicle equipped with on board mobile unit (MDT) interfacing with a radio dispatch system. A Mobile Date Terminal can receive both exclusive and non-exclusive messages. An exclusive message is the one used to offer a job to the operator of one MDT. A non-exclusive message is the one used to send messages to all the MDT units in the system simultaneously. This audible system interface device detects only the exclusive messages.
There are available various conventional telecommunications which do not provide the novel improvements of the invention herein disclosed.